Single-Step Deposition of Cerium-Substituted Yttrium Iron Garnet for Monolithic On-Chip Optical Isolation

Du, Qingyang; Goto, Taichi; Kim, Dong Hun; Aimon, Nicolas M.; Hu, Juejun; Ross, Caroline A.; Sun, Xueyin; Onbaşlı, Mehmet C.

doi:10.1021/acsphotonics.5b00026

Cited by 104 publications

(77 citation statements)

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“…The most promising method for integration of YIG thin films onto non-garnet substrates has been to simply anneal amorphous films made by sputter or pulsed laser deposition [14][15]20,[24][25][26][27][28][29]. High temperatures are required to achieve the garnet phase, and a number of other phases can form with large strains due to thermal expansion mismatch [24,30].…”

Section: Introductionmentioning

confidence: 99%

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Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal

Gage

Dulal

Sølheid

et al. 2017

Materials Research Letters

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Traditional one-step annealing of ultrathin amorphous Y-Fe-O films on Si has been reported to yield 'incomplete crystallization'. Here, it is shown that films produced by standard anneals (e.g.: 800°C, 3 min) actually contain yttrium iron garnet (YIG) crystallites in a nanocrystalline non-garnet matrix. During in situ TEM laser annealing, a low-temperature pre-anneal enabled subsequent YIG crystallization at velocities of 280 nm/s that prevented the formation of the nanocrystalline matrix. From these results, a two-step rapid thermal anneal was identified (400°C, 3 min; 800°C, 3 min) that successfully produces phase-pure garnet films on SiO 2 on Si. IMPACT STATEMENTA novel two-step anneal discovered through in situ TEM laser annealing produces phase-pure, fully crystallized ultrathin YIG films grown on SiO 2 on Si. ARTICLE HISTORY

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Section: Introductionmentioning

confidence: 99%

“…Secondary phases inhibit the formation of garnet and severely hinder device performance. Despite these challenges, polycrystalline YIG has been grown on non-garnet substrates with varying degrees of success [24,[26][27][29][30][31][32]. Thinner films have proven to be exceptionally challenging [24].…”

Section: Introductionmentioning

confidence: 99%

Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal

Gage

Dulal

Sølheid

et al. 2017

Materials Research Letters

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“…Faraday rotation is a nonreciprocal rotation, or mode conversion, that occurs with a magnetic field parallel to the propagating light, and it can provide isolation together with a simple polarizer at the input of a waveguide 20,21 . Almost all of the recent devices in both categories have employed Ce:YIG as the MO material 8,19,[21][22][23][24][25][26] . In the first category, isolators based on Mach-Zehnder interferometers have been developed by bonding Ce:YIG onto Si-on-insulator (SOI) waveguides by surface-activated 18 or adhesive 22 bonding.…”

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confidence: 99%

“…Attempting the growth of Ce:YIG without a seedlayer results in the formation of oxide phases other than garnet without useful MO properties 8 . Recently a one-step YIG/Ce:YIG anneal has also been reported 25 and will be discussed below. In a semiconductor-core device, the waveguide has a higher index of refraction (n≈3) than the garnet layer (n≈2).…”

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confidence: 99%

“…A cross section schematic of the device is shown in Figure 1 (a). Reported Faraday rotation coefficients were used, including 200°/cm 46 for the YIG seedlayer and a range of values (-1100°/cm 25 , -1263°/cm 28 , -3300 °/cm 47 , -3700°/cm 48 , -4500°/cm 31 ) for the Ce:YIG layer. The lower values in this range are attributed to incomplete crystallization of Ce:YIG 28 , 32 .…”

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Optimized Magneto-optical Isolator Designs Inspired by Seedlayer-Free Terbium Iron Garnets with Opposite Chirality

et al. 2016

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2016) Optimized magneto-optical isolator designs inspired by seedlayer-free terbium iron garnets with opposite chirality. ACS Photonics, 3(10), pp. 1818Photonics, 3(10), pp. -1825Photonics, 3(10), pp. . (doi:10.1021 This is the author's final accepted version.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/124482/ ∥ School of Engineering, University of Glasgow, Glasgow, Scotland, U.K. ABSTRACT: ABSTRACT: ABSTRACT:ABSTRACT: Simulations demonstrate that undoped yttrium iron garnet (YIG) seedlayers cause reduced Faraday rotation in silicon-oninsulator (SOI) waveguides with Ce-doped YIG claddings. Undoped seedlayers are required for the crystallization of the magneto-optical Ce:YIG claddings, but they diminish the interaction of the Ce:YIG with the guided modes. Therefore new magneto-optical garnets, terbium iron garnet (TIG) and bismuth-doped TIG (Bi:TIG), are introduced that can be integrated directly on Si and quartz substrates without seedlayers. The Faraday rotations of TIG and Bi:TIG films at 1550nm were measured to be +500 and -500°/cm, respectively. Simulations show that these new garnets have the potential to significantly mitigate the negative impact of the seedlayers under Ce:YIG claddings. The successful growth of TIG and Bi:TIG on low-index fused quartz inspired novel garnet-core waveguide isolator designs, simulated using finite difference time domain (FDTD) methods. These designs use alternating segments of positive and negative Faraday rotation for push-pull quasi phase matching in order to overcome birefringence in waveguides with rectangular cross-sections. KEYWORDS KEYWORDS KEYWORDS KEYWORDS: yttrium iron garnet (YIG) seedlayer, terbium iron garnet (TIG), cerium doped yttrium iron garnet (Ce:YIG) , silicon on insulator (SOI) waveguides, Faraday rotation, optical isolator Photonic systems have ever increasing applications in high-speed electronics/ spintronics 1,2 , computing 3 , telecommunications 4,5 and medicine 6 . These systems use light as the signal carrier, and similar to diodes in electronics, photonic systems require non-reciprocal devices with high optical isolation capabilities to protect light sources. Currently, non-reciprocal photonic materials are only available in discrete components. However, if light sources are to be integrated onto photonic chips, non-reciprocal devices will also be needed on those chips. Indeed, isolators will be necessary anywhere in optical circuits where back-reflections are detrimental and likely to occur. Garnets, with their unique magneto-optical (MO) properties have been the material of choice for building passive non-reciprocal devices [7][8][9][10] . In general, non-garnet non-reciprocal devices are active devices that require external power sources, which increase the complexity and cost of the device [11][12][13][14] . MO effects in garnets are the result of non-zero off-diagonal components in the dielectric matrix (ε) ...

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Magneto‐Optical Bi:YIG Films with High Figure of Merit for Nonreciprocal Photonics

Fakhrul

Tazlaru

Beran

et al. 2019

Advanced Optical Materials

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lator devices is commonly a MO iron garnet material, in particular yttrium iron garnet (YIG, Y 3 Fe 5 O 12 ) with substituents such as Ce or Bi to increase the MO performance. [5][6][7][8][9][10][11][12][13][14][15] However, the integration of garnets on a Si (or other semiconductor) platform is challenging due to the incompatible lattice parameters and the thermal expansion mismatch between garnets and common semiconductor substrates. [6][7][8][9][10][11][12][13][14][15][16] Moreover, crystallization of the garnet phase usually requires a high thermal budget. Garnets formed on semiconductor substrates are polycrystalline and exhibit higher optical absorption than single crystal films. Furthermore, impurity phases such as YFeO 3 , Fe 2 O 3 , and Bi 2 O 3 can form during the crystallization process, [17] which contributes to optical loss. These factors result in inferior optical performance of polycrystalline MO garnet films compared to the bulk garnet material, and a lower figure of merit (FoM), defined as the ratio of the Faraday rotation to the absorption coefficient per length of the material.Considerable work has been done on growth of garnet films on semiconductors to enable demonstrations of isolators and modulators. [6][7][8][9][10][11][12][13][14][15][16] The first monolithically integrated optical isolator [6] used 80 nm thick Ce:YIG which was grown by pulsed laser deposition (PLD) on a pre-annealed 20 nm thick YIG seed layer to induce crystallization of the Ce:YIG. A simplified PLD process was introduced by Sun et al. [11] where the YIG seed layer was placed on top of the MO garnet and both layers were crystallized simultaneously by rapid thermal annealing (RTA). This top-seedlayer process places the MO garnet in direct contact with the underlying Si waveguide, maximizing the coupling of light from the waveguide to the MO cladding, but it has only been applied to Ce:YIG. Recently rare-earth garnets have been developed that crystallize on Si and quartz without a seed layer, including sputter-deposited terbium iron garnet (TIG) and Bi-doped TIG (Bi:TIG). [18,19] Growth of MO materials on the sidewall of the waveguide can enable a wider range of device designs, including isolators for transverse electric (TE) polarization. Integrated semiconductor lasers emit TE-polarized light, and TE mode isolation using NRPS requires placement of the MO material on the sidewall of the waveguide to break left-right symmetry. [18,20,21] However, the NRPS-based integrated optical isolators that have been experimentally demonstrated are made with the MO material on the top or bottom surface of the waveguide, which isolates only the transverse magnetic (TM) polarization. [6][7][8][11][12][13][14] It is therefore essential to establish deposition conditions that yield Thin film magneto-optical (MO) materials are enablers for integrated nonreciprocal photonic devices such as isolators and circulators. Films of polycrystalline bismuth-substituted yttrium iron garnet (Bi:YIG) have been grown on silicon substrates and waveguide d...

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Single-Step Deposition of Cerium-Substituted Yttrium Iron Garnet for Monolithic On-Chip Optical Isolation

Cited by 104 publications

References 39 publications

Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal

Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal

Optimized Magneto-optical Isolator Designs Inspired by Seedlayer-Free Terbium Iron Garnets with Opposite Chirality

Magneto‐Optical Bi:YIG Films with High Figure of Merit for Nonreciprocal Photonics

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Single-Step Deposition of Cerium-Substituted Yttrium Iron Garnet for Monolithic On-Chip Optical Isolation

Cited by 104 publications

References 39 publications

Si-integrated ultrathin films of phase-pure Y3Fe5O12 (YIG) via novel two-step rapid thermal anneal

Si-integrated ultrathin films of phase-pure Y3Fe5O12 (YIG) via novel two-step rapid thermal anneal

Optimized Magneto-optical Isolator Designs Inspired by Seedlayer-Free Terbium Iron Garnets with Opposite Chirality

Magneto‐Optical Bi:YIG Films with High Figure of Merit for Nonreciprocal Photonics

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Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal

Si-integrated ultrathin films of phase-pure Y₃Fe₅O₁₂ (YIG) via novel two-step rapid thermal anneal